This is a utility application based upon provisional application Serial No. 60/263,894 filed Jan. 24, 2001 entitled xe2x80x9cPremixed Calcium Phosphate Cement Pastesxe2x80x9d for which priority is claimed.
This development was supported in part by USPHS Research Grant DE11789 to the American Dental Association Health Foundation from the NIDCR. The United States or an agency thereof may therefor have certain rights to the claimed invention.
A self-hardening calcium phosphate cement, consisting of tetracalcium phosphate (TTCP) and anhydrous dicalcium phosphate has been shown in clinical studies to be efficacious as a bone repair material. The hardening time (HT) of the cement is about 30 minutes when the powder constituents are mixed with water and 5 minutes when mixed with a phosphate solution as the liquid. Hydroxyapatite (HA) is the major product formed as a result of the mixing and hardening. In recent years, additional calcium phosphate cements (CPC) that do not contain TTCP have been developed, e.g. xcex1-tricalcium phosphate (TCP) and CaCO3; dicalcium phosphate (DCPA) and Ca(OH)2). These cements harden in 10 minutes when mixed with a phosphate solution, and they also form HA as the final product.
A cement paste of the type referenced mixed with glycerol was studied for root canal filling, sealing, and injectability and it was reported that the glycerol-calcium phosphate cement (CPC) paste showed better biocompatibility than a number of presently used root canal filling or sealing materials. However, the prior art did not teach a paste material useful as a bone cement that remains stable over a period of time and hardens only when delivered to a desired site.
The present invention comprises compositions and means for formulating premixed glycerol and calcium phosphate cement pastes that are stable in a package, resist washout, and will harden only after being delivered to the defect or implant site. Glycerol was used as the liquid because the CPC hardening reaction to form HA does not occur in a water-free environment. Hydroxypropyl methylcellulose (HMC) and Na2HPO4 were also added to improve the paste cohesiveness and accelerate cement hardening upon delivery to a desired repair site.